为提高效率，提问时请提供以下信息，问题描述清晰可优先响应。
【DM版本】:
【操作系统】：
【CPU】:
【问题描述】*：```language
[dmdba@localhost dev]$ /dmdb8/dmdbms/bin/dmasmcmd
DMASMCMD V8
ASM>listdisks /dev/dm
[/dev/dm/asm-dmvote]: Used ASM disk, name:[DMASMvote], size:[1024M], group_id:[125], disk_id:[0]
[/dev/dm/asm-dmdcr]: Used ASM disk, name:[DMASMdcr], size:[1024M], group_id:[126], disk_id:[0]
[/dev/dm/asm-dmdata]: Unused ASM disk, name:[DMASMDATA0], size:[10239M]
[/dev/dm/asm-dmarch]: Unused ASM disk, name:[DMASMARCH0], size:[10239M]
[/dev/dm/asm-dmredo]: Unused ASM disk, name:[DMASMREDO0], size:[10239M]

总共5个磁盘为啥前两个可用最后3个不可用呢？